An information search is a procedure of providing an appropriate response for a query of user based on specific knowledge and information. For example, when a query for finding a specific program is inputted to a smart television system, a response to the query may be provided to the user by accessing a knowledge information database storing a TV program through information search. However, a knowledge information database which has been used in the conventional information search methods is a relational database, and, in this case, there is a problem that appropriate information cannot be searched if a query is not provided in a format which is the same as that of information stored in the database. Also, when the query has a complicated format which needs semantic inference to be understood, there may be a problem that the appropriate response cannot be searched. For example, if we provide a query ‘let's see a soccer game of Ji-Sung Park’ to a smart TV system, we cannot obtain a query result ‘Asian cup’. The reason of the above problem is that an article of ‘Asian cup’ does not include information related to ‘Ji-Sung Park’. In order to perform the above query correctly, information that Ji-Sung Park is participating the Asian cup is additionally necessary. Although ontology is used as a solution to consider the above semantic matters, it is a very difficult task to construct and manage the ontology, and it is impossible to construct so many ontologies for inferring queries related to knowledge information. Also, there is a limit in reflecting information which are changing in real time.